Recent Advances in Integrated Design and Manufacturing in Mechanical Engineering

This paper describes a process improvement study undertaken at three sites of UK electromechanical engineering companies, using a derivation of the Carnegie-Mellon/SEI Systems Engineering Capability Maturity Model ®(SE-CMMSM) called the Process Capability Model — Mechanical Design (PCM-MD). The model was applied within a traditional engineering discipline domain, namely mechanical design. The new assessment tool was piloted on a sample of nine mechanical engineers and eight design engineers as well as some ancillary functions, such as stress and thermal analysis. This was expanded to take into account the views of the downstream manufacturing disciplines and was then subsequently rolled-out into the other companies. The results from these studies support the view that the SE-CMM can be adapted and used in CMM-type assessments for mechanical design process benchmarking.Key words:

Engineering designers make many design decisions for selecting optimal options based on insights into underlying relationships among design parameters under consideration. As design proceeds, more and more design parameters are introduced and concretized. The increase of design parameters poses challenges and difficulties for designers to gain deep and rich insights, and to make informed design decisions. Designers therefore need to be adequately supported to explore design alternatives to search for the optimal one. This research aims to provide design support tools for gaining better insights, and to integrate them into a design support system that facilitates designers’ exploration of design solutions. To achieve this aim, new constraint solving methods based on generic and rigorous principles of symbolic algebra have been derived. These methods overcome difficulties of conventional methods, and provide necessary and sufficient information for making insightful design decisions. The advantages of this approach will be shown through a case study.

Engineers use many different models in the course of their work, varying from physical models through graphical to mathematical and computational models. This paper describes a study of the automobile body-in-white design process to identify the models used in the course of this process. It explains the experimental method of using Petri net diagrams to describe the design process in an automotive company, and then using these models in conjunction with the company’s engineers to identify the models used by the engineers at each stage in the process. It will describe the overall use of models in the process, and also one particular aspect of the process in some detail, to illustrate the application of the experimental technique. Representations involve the initial use of sketches and stylists’ renderings, then the development of the body form through physical models. Specialist models are used for formability and structural analysis, and for the development of tooling. The paper concludes with some suggestions on the lessons to be learned for process modelling and computer support tools.

In this paper, we present an application of Genetic Algorithm (GA) in Computer Aided Process Planning (CAPP). Sequencing of machining operations is an important function in process planning elaboration. It conditions the choice of machines, the feasibility and the cost of the process plan. We suggest a GA that allows the handling of conditional precedence constraints, the representation of different process planning solutions and the discovery of alternative optimized solutions. The formulation of planning problem covers resources like machine-tools, set-ups and tools. We assumed that resource information is provided either automatically or interactively. Sequencing is performed using ordinal representation and Tool-Set-upMachine’s triplets using a domain specific integer coding schema. The influence of the different parameters such as the population size, the probabilities of mutation and crossover, local search methods on the evolution of the population are presented.

In many practical situations, it is necessary to have reliable evaluations of local quantities. For example, this is the case in design where dimensioning criteria nearly always involve local quantities (stresses in specified zones, Von Mises’ stresses, displacements, stress intensity factors, ...). In current industrial practice, these quantities are evaluated using F.E. analysis. Even if the mechanical model chosen is adequate (good description of the geometry, good knowledge of the material’s characteristics and of the loading), the F.E. analysis introduces errors in the quantities being calculated. For the engineer, it is essential to study and, if possible, to evaluate the quality of the calculations carried out in order to validate the results. In this work, we are concerned with the quality of a linear F.E. analysis. We propose a tool, based on the concept of error in constitutive relation, which enables one to evaluate the local quality of the stresses. We show that this approach gives good results.

The paper focuses on the design of wire harness assemblies for mass customization by a delayed product differentiation. In order to manufacture broadly diversified products, two algorithms are proposed both using a generic representation of wire harness with all options and variants in order to produce each wire harness in a short period of time. An industrial case study is presented in a contractor/supplier context, where the supplier must respond in a short time and provide a totally diversified product, which is to be delivered according to the specifications provided by the contractor. In the particular case described above, two different algorithms are applied and compared.

This paper presents a unified model for computer-aided tolerancing. It combines the benefits of the Jacobian matrix model and the torsor (or screw) model. The former is based on small displacements modeling of points using 6x6 transformation matrices of open kinematic chains in robotics. The latter models the boundaries of 3-D tolerance zones resulting from a feature’s small displacements using a torsor representation with constraints. The proposed unified model expands the functionalities of the Jacobian model under two important aspects. First, the punctual small displacement variables of the former Jacobian formulation are now considered as intervals formulated and solved using interval-based arithmetic. The equations describing the bounds within which the feature is permitted to move, which are the constraint equations of the torsor formulation, are applied on the unified model. Second, some of the small displacement variables used in the model are eliminated due to the invariant nature of the movements they generate with respect to the toleranced feature. This standard result of the torsor formulation is applied to the unified model. The effect of this is to significantly reduce the unified model size. A example application is also presented.

For several years, CAD software have adopted a variational approach for modelling. This choice is justified by users’ needs. Indeed, a product is often designed to fulfill requirements that are not expressed as geometric specifications. In addition, the geometric model of the product evolves continuously during the design process. During this process, the software must be able to preserve the coherence of the model specifications. To fit into this context, a variational modeler has been set up which includes new concepts of analysis and solving approaches to identify locally over/under-constrained systems and provide more feed back to the designer. The structure of the modeler is briefly outlined followed by the introduction of the analysis and solving modules that are clustered into three tasks: a pre-solver analysis, a solver, a post-solver analysis in case of resolution failure. Parts of examples are used to illustrate the descriptions of this structure.

In the case of assembled products, tolerancing is a key factor for quality and reliability. Traditionally, tolerances are defined by an interval [LSL; USL]. Several approaches have been proposed to determine this tolerance, the main results of which be referred. Inertial Tolerancing consists in tolerancing the mean square deviation from the target rather than the distance. This alternative has numerous advantages over the traditional approach, particularly in the case of product assembly, mixed batches and conformity analysis. In this paper, we will detail “inertial tolerancing” and compare both approaches: traditional and inertial tolerancing.

We propose in this paper the premises of an Interactive Decision Support System dedicated to the unidirectional tolerancing of mechanical assemblies. The foundation of our work is an efficient representation of a mechanical assembly based on graph theory. From this model, we can determine all the configurations of an assembly. An extended syntax for the functional constraints permits then to generate automatically all the tolerance chains. The final result is an automatically generated linear system of equations and inequations expressing the tolerance chains, as well as the existence of the configurations and coherence of the dimensioning scheme. This system can then be solved by an analysis or a synthesis approach.

In the framework of transport industries, vehicle design optimisation represents a key priority issue. Indeed, this is a result of the huge pressures imposed on industrialists particularly in terms of active safety. Moreover, among of all the materials used for design, some such as composite materials require special attention. It is consequently within this framework that we propose to describe in this paper the contributions which were made to the numerical simulation tools for structural analysis. The latter can involve crash type loading for example. In a first instance, certain behavioural phenomena and their integration into the computational code will be described. Secondly, some elementary validations will be presented. Finally, some applications relating to the dimensioning of panels in composites subjected to linear or point impacts will be revealed. The conclusions of these studies will enable us to show, on the one hand, a certain reliability of the developments which permit their use as design tools but also, on the other hand, to foresee the prospects of future research.

This paper presents several results regarding the kinematic calibration of a Stewart platform. Firstly, a general method for the precision modeling of parallel robots is proposed by the authors and applied in the case of the Stewart platform. Thus, an accuracy model of the Stewart platform is established, taking into account the errors of the geometrical parameters. Next, on the basis of the precision model and the experimental data for the accuracy of the Stewart platform, some algorithms used in kinematic calibration were generated and tested; overcoming some numerical difficulties, the actual deviations of the geometrical parameters were identified. Thus, the correct values of geometrical parameters and, implicitly, the correct kinematic model used in command/control were obtained. Finally, the importance of the calibration in the optimization of the kinematic models is emphasized, based on the numerical results. According to these aspects, the accuracy of the Stewart platform model was significantly increased.

This paper deals with a special class of three-degree-of-freedom parallel manipulators. First, the singular configurations of the two Jacobian matrices are studied. The isotropic configurations are then found based on the characteristic length of this manipulator. The isoconditioning loci for the Jacobian matrices are plotted to define a global performance index allowing the comparison of the different working modes. The resulting index is compared with the Cartesian workspace surface and the average of the condition number.

The elastokinematic performances of automotive axles guarantee driveability and security of passengers, also giving vehicles improved road-holding properties as well as increasing or reducing briskness. The search for improved performances leads to optimisation of mechanism kinematics. It also concerns integration of suitable bushings, which are elements in standard cars that are vital for passenger comfort in that they filter out vibrations. Such optimisation is needed since the design does not incorporate active suspension technologies. This paper presents a fast and efficient method which has been applied to the multi-criteria problem characterised by a large number of variables. It takes into account intended judicious specifications as well as inherent constraints to incorporation in the vehicle.

The present article investigates self-loosening of bolted assemblies under the effects of transverse loads. Firstly, we discuss the relaxation phenomenon that occurs at the end of tightening. We then perform modeling and calculus for self-loosening conditions for a short screw, neglecting the tilt of the screw in its tapping. In particular, we determine a maximum value for the friction coefficient such that this self-loosening occurs. Lastly, we indicate the procedure to confirm these results and to extend the study to the case of long screws.

In the automotive passive safety field, numerical simulations gradually replace experimental crash-tests, and allow through parametric studies an improved definition of the architecture and the sizing of vehicles. In this context, this paper is focused on a methodology for crashworthiness optimization. After a review of difficulties inherent to the numerical modeling, we propose a global optimization strategy based on a surrogate approach: the resolution of the real optimization problem is replaced by a sequence of resolutions of approximate problems. An interpolation model is adopted in order to smoothen the objective function and constraints and to enable the analytical calculations of their gradients. The response surface model is build by a stochastic process. Unlike traditional techniques of construction of polynomial response surfaces by least squares regression, the approach developed, based on Sph (smooth particle hydrodynamics) methods, makes it possible to reproduce strong nonlinearities of the objective functions and limiting constraints. Moreover, the flexibility of these models allows the updating of the approximation during the optimization process, which makes it possible to improve locally the quality of the approximations. We compare the quality of the approximations for various types of optimal design of experiments.

In this study, a multidiscplinary optimisation methodology of composite structures with the Resin Transfer Moulding (RTM) process is suggested in order to satisfy both the structural and the process requirements. Among the composite manufacturing techniques, the RTM process is distinguished for its own many advantages such as low manufacturing costs, complex shapes, high productivity, and good mechanical performance. In designing composite structures with the RTM process, tailoring the fibre preform architecture plays an important role as well as deciding the injection strategy. With some appropriate assumptions, a simplified optimisation method is suggested to find a near optimal design configuration. At first, the number of fibre mats, the stacking sequence of layer angles and the injection gate locations are found in order to satisfy the structural criteria, such as the stiffness requirement, and the process criteria, such as the mould filling time. Then, the thickness of the composite laminate and the fibre volume fraction are determined so as to reduce the weight keeping all the design criteria satisfied. This problem is a multi-objective optimisation problem and hence an objective function is appropriately formulated. As an optimisation technique, a genetic algorithm is used. The reliability of the present design methodology is assessed with some examples.

This paper describes an approach of generating feasible design solutions in terms of form features according to functional requirements of sheet metal component design. The objective of this research is to develop a methodology of generating a solution space at the conceptual design stage and subsequently selecting an optimal solution for sheet metal component design. A decision made at the conceptual design stage causes consequences for all subsequent phases of the product life cycle. Normally a concept or a principle solution is selected on the basis of desired functional requirements, neglecting the consequence of selection on the performance of other life cycle phases like manufacturing and assembly etc. This approach causes problems at later product realization stages in terms of cost & time incurred due to redesign of product. This paper presents a novel approach of how consequences caused by design decisions on later life cycle phases specially manufacturing can be brought to the attention of designers at the conceptual design stage of sheet metal components

The 3D simulation of objects in an evolutionist environment is hard to implement when we consider the amount of parameters and the high cost of computer resources. These facts bring us to introduce the notion of associated fuzzy volumes. This concept is based on the fuzzy geometry principles, which can be used in production with robots assistance. The technique is the associating to complex objects and their environment some fuzzy volumes, constitute of peaks network (points positioned in 3D). In which these points are situated around an object or on its surface in order to approach a target object. With the algorithm developed in this paper, which is based on a genetic algorithm, it is possible to detect interference during the simulation time. The Nc machining is used application of this technology

In the field of manufacturing a great number of industrial software tools integrate a cutting tool modeling. For some cases the cutting tool is considered as a resource for the various functions of the company. For other experts, it is for supplying the cutting parameters using data bases or experimental and numerical methods. The concept of Tool Material Couple (TMC) is one of these methods. To improve the performance of manufacturing systems, one has to facilitate collaborative work by developing tools for the concurrent engineering. The presented study is situated in this frame and proposes a normalized data model. This generic model based on the product structure model of the STEP standard uses the TMC concept to test its validity as consensual definition of the cutting tools and the cutting parameters. We also demonstrate that improvements of the concept TMC are necessary to consider the new cutting technologies, such as Hard Turning.

Determination of build orientation for layer-based manufacturing (LM) can be considered as a multi-criteria optimization problem. The preferred build orientation should have the tendency to maximize surface quality, minimize build time and build cost simultaneously. For a given part model, different build orientation will result in variant surface quality, support design, number of stock layer, removed material volume and part stability. In this paper, determining the build orientation is modeled as a fuzzy decision making problem. Fuzzy sets are employed to rate the contribution made by alternatives. The preferred orientation is then chosen according to its rank in the result of fuzzy synthesis evaluation.

The flank milling of complex forms is a very effective process from the point of view of productivity and surface quality. Many works deal with research on the optimal positioning of the tool which is considered as a rigid body in order to minimize tool path errors. The purpose of our work is to integrate the compensation of the tool distortions in this optimal positioning calculation. In flank milling with long tools, the distortion of the cutter generates a significant wave (that can reach 0,6mm) on the machined surface due to the effects of the helical angle and the radial force which varies during the cutter rotation. After detailing an analysis of the force evolution and the associated model calculation, we will present a test protocol, that can be implemented in industry, in order to characterize the model parameters as a function of the couple tool-workpiece material. Then we will present a test to assess our prediction model of the straightness defects of the machined surface according to all machining parameters. These results make it possible to make up for defects by applying a translation to the tool in 3-axis and by applying a translation combined with a rotation in 5-axis milling.

An extensive study has been undertaken to investigate the tool-wear mechanisms of CBN cutting tools in finish machining of the following hardened steels: X155CrMoV 12 cold work steel (AISI D2), X38CrMoV5 (AISI H11) hot work steel, 35NiCrMol6 hot work steel and 100Cr6 bearing steel (AISI 52100), treated at 54 HRC. A large variation in tool-wear rate has been observed in machining of these steels. The generated tool flank grooves have been correlated with the hard carbide density of the workpieces. A crater wear study has also been performed and, it is shown that the appearance of an adhered third body could induce a chemical wear in the tool.

Crimping is a classical technology process to ensure the electrical and the mechanical link between a wire and a connector. Numerical modelling of the process is helpful to choose and to optimize the dimensions of the crimping part of the connector. In this paper, we discuss a 2D simulation of the crimping process, using implicit and explicit finite element methods (ABAQUS/Standard and ABAQUS/Explicit) and we compare the results with experimental data from the industrial process of crimping (geometry, shape, surfaces and punch force). This non-linear problem involves large elasto-plastic strains and multiple contact conditions, with friction between the strands and the grip. One of the major difficulties of the simulation is due to the definition of all possible contact couples between strands. The explicit method is preferred for the modelling of multi-contact problems, in spite of the quasi-static process of crimping. Thus, some simulations with the implicit method have been performed to compare the results and tune the simulation parameters of the explicit approach (space and time discretization). Subsequently, parametric studies are performed to show the effect of the friction ratio or the position of the strands in the wire.

Highly-stressed steel components, e.g. gears and bearing parts, are appropriate applications for hard turning. Therefore the process effects on significant engineering properties of work materials have to be carefully analyzed. Roughness, residual stresses and white layers as parts of surface integrity, are function of the machining parameters and of the cuttability of the cutting edge, i.e. of the tool wear. The aim of this work was to study the influence of feed rate, cutting speed and tool wear on the effects induced by hard turning on case-hardened 27MnCr5 gear conebrakes and to point out the technical limitations in mass production.

The use of the complex shaped profile parts is very frequent in automobile and aircraft industries. A general manufacturing process is the stretch forming of a rectilinear workpiece over a die. This presentation proposes a simplified method to model and simulate the stretch forming process of 3D profiles. The profile is represented as a curved beam complying with the Bernoulli’s hypothesis. This simplified model, taking into account the forming limits related to the defects appearance (fractures, wrinkles...), allows finding the laws of the profile end displacements and the forces to be applied. The simplified simulation method is being confirmed by the comparison with the results of the finite element analysis. The highly reduced calculation time and the ordinary necessary computer resources authorize the joint utilization of this simulation software and software controlling the stretch forming presses.

The optimisation of cutting conditions in High Speed Machining (HSM) requires the use of a vibratory approach in order to avoid a fast deterioration of the tool and of the spindle, as well as a loss of quality of the surface finish. We suggest a transposition of the method of stability lobes to the case of milling thin parts, which is very typical in the aeronautical manufacturing context. After having modelled the dynamic behaviour of a blade and of the cutting efforts in side milling, we describe the zones of machining instability. An experimental validation allows us to emphasise the transition from stability to instability, in accordance to our theoretical results. The experimental profile is then compared with a computed profile. A decomposition of the different situations of contact between the tool and the part permits us to show the influence of back cutting in the model. Tests of machining then permit the quantification of its role. The objective of this work is the definition of a quick methodology for determining the optimal cutting conditions in a given industrial machining configuration.

To optimize the cutting conditions in machining, it is necessary to quantify the energy parameters involved in the process. Thus the control of a cutting process is realized if the cutting parameters, the kinematic parameters and contact actions are accurately estimated. To estimate these parameters, original metrological devices have been developed in the various laboratories involved in this study. Force and moment measurement has been carried out using a six component dynamometer [4]. Various image processing techniques allow to determine the chip/tool contact surface and the chip ejection angle. Complete and detailed energy equilibrium realized with those devices has clearly demonstrated the influence of moments on the mechanical power consumed by the cutting process. With these results, a three-dimensional thermomechanical cutting model has been developed. The originality of this model is the complete and continuous definition of the tool geometry, integrating tip ray and edge acuity characteristics. Forces and moments, chip kinematic parameters (chip orientation, tool/chip contact area) can be evaluated. The presented study shows the geometrical and kinematic parameters effects, such as the penetration rate on force and moment values in turning. A correlation is established between kinematic parameters, forces, moments and an original experimental study using an imagery interpretation method.

For higher productivity and product quality, it is necessary to know the accuracy of machine tools so that defective parts are not manufactured. Angular and positioning errors are quite common problems in machine tools. The origins of these errors are kinematic parameter deviations resulting from manufacturing errors, assembly errors or quasistatic errors. By static measurements such as laser interferometer, linear comparator (Heidenhain VM182), electronic inclinometers (Wyler Leveltronic) and dynamic measurements (Double Ball Bar, DBB) different kinds of error origin information of the machine tools can be obtained. It is possible to convert the measurement results of one method to another with certain degree of accuracy. This helps to justify the correctness of the measurement method and locate the error origins more precisely. This study shows a mapping between static and dynamic measurements of machine tools by calculating tool tip errors using different devices as mentioned above. For static measurements the laser interferometer, VM 182 and Leveltronic measuring systems and for dynamic measurements the DBB has been used in this study. Theoretical trace for DBB is obtained based on roll, pitch, yaws and positioning errors found by laser, VM182 and Leveltronic measurements. These traces are compared and simulated with the trace obtained by DBB.

The geometric error measurement techniques for machine tools have not evolved for several years. The laser tracker, a three-dimensional portable measuring system, opens the way to automatic measurements and consequently, the possibility of positioning error compensation under acceptable economic conditions. We propose strategies of measurement and treatment to improve and control the measurement uncertainty of a laser tracker used as a system of calibration within the framework of the analytical model of global compensation by grid.

High speed machining is really suitable for present production constraints. However high rotational speeds inherent to high cutting speeds excite structures at high frequency. Resulting dynamic phenomena can reduce surface quality, damage material and decrease productivity. So as to avoid machining cutting conditions leading to the development of such phenomena, we developed a tool allowing the numerical computation of the machining system dynamic behaviour as well as to predict the machined surface geometry and quality. Our approach is based on the numerical computation at the macroscopic level of workpiece-tool system dynamic behaviour submitted to cutting forces. These forces are modelled and allow us to deduce the workpiece motion thanks to the Newton equation which is solved with an implicit integration scheme. The cutting nonlinearities are taken into account by the modelisation of the surface being machined. Simulation results follow the experimental trends, and a machining simulation example is given to show the main regenerative vibration effects upon the behaviour of machining system as well as upon the surface quality.

This paper presents an automatic feature shape recogniser tool for a Design For Assembly (DFA) methodology. For each part of a product, this feature research is performed into two steps. First, weight, dimensions and symmetries are identified and the part is classified as rotational or not. Second, form features, like steps or grooves, are extracted in order to estimate the orientation efficiency of the part. To fulfil first step requirements, an optimal bounding box, in the context of DFA, is found using the boundary representation (B-Rep) model of the part. The proposed algorithm is based on a topological exploration and on geometric properties of faces. 2D features identification step operates on a simple vertex-edge polyhedral model of the part. On every plane projection, along an axis of the bounding box, outer wire analysis serves as starting point for the 2D feature recognition. Finally, a 2D feature selection procedure, that optimises the orientation efficiency, is presented. All these algorithms are implemented in “FuzzyDFA”, an assembly-oriented computer aided design software that takes advantage of a fuzzy decision support system.

We have developed the nodal pre-optimization concept in the context of our work on finite element analysis and CAD/CAM integration. This concept consists in deriving from all engineering data (geometric features, discretization error, boundary conditions, materials and physical constants) a nodal density map for automatic mesh generation. Nevertheless, this concept can only be applied if a mesh generator is able to satisfy precisely the density map mentioned above. This is the reason why we have developed a 3D automatic mesh generator based on advancing front techniques, featuring a strong ability to respect an imposed variable density map. After a brief description of the process, we introduce new parameters related to the density map respect. A set of applications of the concept to industrial mechanical parts are also presented in the paper.

Numerical simulations of mechanical phenomena using the Finite Element approach are extensively used in industry. On one hand, the FE models manipulated are evolving toward a high complexity in terms of size (number on FE elements in the model) and phenomena addressed (non linear behaviour laws, time dependent simulations, ...). On the other hand, design methodologies are evolving towards computer supported collaborative work. The paper proposes a concept of a visualization model for the analysis and collaborative work around FE simulations results. The model presented takes into account the configurations and the equipment characterizing the use of these results and is based on a decimation technique to reduce the size of the FE model. To compress the model even further, it is covered with textures generated from the FE solution. In order to generate this visualization model in a transparent manner for the analyst, automatic partitioning methods have been set up. The compactness of the model is addressed using a multi-resolution approach on user-defined threshold values to extract the most significant part of the simulation results.

Systems Engineering (SE) was born in 1960’s at NASA to solve issues due to the increasing complexity of products developed in the space industry. Nowadays, the automotive industry is adapting and introducing SE. In addition to early applications, car production basically provides a complex and mass product, which is also characterized by high diversity. This specificity obliges us to review the role of manufacturing systems in the SE methodology described in international standards. This article has three major aims: the first aim is to define SE’s span versus other industry’s design methodologies, comparing concepts and scopes; the second aim is to give an approach of SE applied to manufacturing systems, especially requirement engineering and architectural design; the third aim is to highlight benefits expected from a level-defined application of SE.

Engineering Changes (EC) implementation in product definition and at all stages of the product life cycle cannot be avoided when struggling for innovation and maintaining the product in accordance with the contractually agreed specifications. These “micro” design actions usually provide large profits on both product and processes and allow a flexibility that Concurrent Engineering requires. If EC management looks a rather simple activity for organizations offering small products on the market, it gets more complex in industries such as aeronautics or automotive industry where the whole supply chain can be impacted. In such industries, this key process remains difficult to control as few performance indicators exist. This lack of measurement does not enable any corrective action to be undertaken. In this paper, an overview of EC management for complex products is presented from the experience we have gained in the aeronautics and automotive industries. First, potential causes and consequences are presented and a generic process for EC management is proposed. Then, the importance of measuring the performances of such a process is highlighted in order to identify any room for improvement. Afterwards, our approach to design and implement a measurement plan for EC processes is detailed. A significant set of indicators and measurement is proposed and discussed according to the specific process we have focused on.

The design process is a crucial phase in the life cycle of an industrial system. It requires the co-operation of different specialists with the skills and knowledge vital to the creation of objects satisfying the needs of the future users. In the case of industrial systems, one of these needs is the safety of those who act on the system during its life. In this paper, we propose a new design approach aimed at correctly integrating all the factors linked to the real contexts of use of the industrial system. The design method is based on a conceptual data model that has already been presented, namely the generic model of the working situation, and therefore only the essential elements will be reviewed to allow a better understanding of the fundamentals of our work.

Scaling up computational mechanical behaviour from small scale to the industrial level within a company gives rises to new problems: lack of back tracing, lost knowledge, repeated mistakes. The work shown in this article aims at identifying, structuring and formalizing the information and knowledge on simulation, to make them capitalisable and reusable by other participants and on other projects. The Renault Company is an active partner in this research through one of its computational mechanics departments and helped us to test and confront our ideas with real industrial simulation processes. The outcome is presented in two main steps. In the first one, we show how the need for structure in simulation processes leads to specification of new links between the different kinds of capitalised information. In the second one, we precisely describe the concept of Instructional Case, whose target is to manage knowledge of a generic nature with a high potential for reuse.

This article presents the specifications and features of a new tool designed to co-ordinate the development of new solutions during the early phases of design projects. It is the result of 18 months of field work during which we played an active role in the development of an innovative solution. We were also able to closely analyze the activities of certain actors (called materials experts) who are often behind proposals for new materials and processes. The ID2 (Innovation Development and Diffusion) tool is geared on the one hand to help innovative solutions emerge, and on the other to consolidate these solutions by circulating them to the company’s different specialists on the other. The tool is based on a concepts/criteria table enabling the viewpoints of the different actors involved to be summarized during the design phase. In this article we shall show how functional features such as links, questions, alarms, information enquiries and the possibilities for exchanging information between actors can contribute to developing solutions for these different professionals. We will also see how the “innovative” solution proposed can be developed further by comparing and assessing it in relation to a list of criteria which is gradually drawn up by the actors involved in the project. This tool is designed to be managed by a specific actor (a coordinating actor), who may also, depending on his/her strategy, consolidate the proposal by involving an increasing number of people.

The mechanical behavior of thin axisymmetric shells subjected to buckling largely depends on variability (loading, material properties, geometrical imperfections,...). The design of this kind of structure is traditionally based on deterministic analytical calculations and on the use of the well-known empirical safety factors listed in the British Standard BS5500 [1]. This empirical standard could be improved by a probabilistic design rule based on the use of the λ _a knock-down factor, which only takes into account geometrical imperfections, and on the use of n partial safety factors noted γ _i which consider all the structural variability except geometrical imperfections. The Arbocz method used to calculate the λ _a -factor has been efficiently applied [2] to an industrial axisymmetric shell requiring a tool which links two types of software: INCA-STANLAX for the numerical finite element mechanical modeling and RYFES for the calculation of the reliability level. This present paper focuses on the γ _i -factors. The calibration of partial factors is treated, with the aim of proposing values to bring to the design rule for thin shel1 structures subjected to buckling.

This paper reports on an investigation into the causes of error in the design process based on a series of case studies in three companies. An initial study attempted to identify the points of occurrence of error in the case studies based on formal process models of the design activities. However, it was found to be difficult, if not impossible, to make a clear identification of a point of introduction of error in any of the case studies. In general, there was no single error source, but instead there was an accumulation of a number of contributory factors that when combined led to the error situation. Furthermore, it was generally not process issues that led to error but human factors. The paper identifies four categories of error inducing circumstance: unrecognised change of circumstances; lack of design effort; lack of integration of information and want of knowledge. Overall, it is asserted that the underlying issue is one of uncertainty handling and risk management.

In this paper we develop an as-yet-missing theoretical framework as well as a general methodology for model-based robust design. At the outset, a distinction is made between three sets: the set of design variables, grouped in the n-dimensional vector x, which are to be assigned values as an outcome of the design job; the set of design-environment parameters (DEP), grouped in the v-dimensional vector p, over which the designer has no control; and the set of performance functions, arrayed in the m-dimensional vector f, representing the functional relations among performance, design variables and DEP. Resorting to the mathematical model available for the object under design, an m × v design performance matrix F, mapping the space of relative variations of p into that of relative variations of f, is derived. Moreover, two pertinent concepts are introduced: the design sensitivity matrix, which plays a major role in the transmission of the variations of p into variations off, and its associated bandwidth, defined as the logarithm of the square root of the ratio between the maximum to the minimum singular values of the design performance matrix, measured in decades. A result stating the relation between the bandwidth of a matrix and its inverse is shown. Consequently, the aforementioned bandwidth represents an index for evaluating the robustness of a design. To demonstrate our approach, case studies are included

This paper deals with a method to analyze the modal characteristics of structures including bounded uncertain parameters. These parameters can be uncertain, variable or not set at a design stage. We will use interval theory to propose a formulation adapted to finite element mechanical problems, taking into account the construction of mass and stiffness matrices. We will consider two kinds of problems: finding the bounds of static problem solutions, and the envelopes for transfer functions. A new numerical method will be used, based on the formulation proposed above. We will emphasize the efficiency of this method on simple mechanical problems. A frame structure will be studied, for which an overlap phenomenon appears on the transfer function envelope.

High technology designs aim to define the best compromise between cost and safety. The Reliability-Based Design Optimization (RBDO) allows us to design structures which satisfy economical and safety requirements. However, in practical applications, the coupling between the geometrical modeling, the mechanical simulation, the reliability analyses and the optimization methods leads to very high computing time and weak convergence stability. Traditionally, the solution of the RBDO model is achieved by alternating reliability and optimization iterations (sequential approach). This approach leads to low numerical efficiency, especially when the structure geometry is described by efficient CAD models (such as B-spline or NURBS) which necessitate a great amount of data. In this case, the integration of the sequential RBDO approach with Finite Element Analysis requires lengthy computing time. In order to avoid this difficulty, we propose an efficient method, called the hybrid RBDO method, based on the simultaneous solution of reliability and optimization problems. In this paper, the efficiency of the proposed methodology is demonstrated on a finite element problem using CAD model description.

The design and manufacture of complex Engineer-to-Order products is characterised by uncertain operation durations, finite capacity resources and multilevel product structures. Two scheduling methods are presented to minimise expected costs for multiple products across multiple finite capacity resources. The first sub-optimises the operations sequence, using mean operation durations, then refines the schedule by perturbation. The second method generates a schedule of start times directly by random search with an embedded simulation of candidate schedules for evaluation. The methods are compared for industrial examples.

Simultaneous design and manufacture planning of new products can offer significant benefits across the product life cycle, such as reduced lead-time, more efficient manufacture, and lower costs. Research at the University of Leeds has focused on developing a new method for achieving this through the use of decision-support tools. These tools will help designers identify suitable manufacturing routes for their product, allowing early manufacturing planning and feedback so that designs can be made more suitable for manufacture. These tools will be underpinned by a series of units, each representing a set of design requirements or process capabilities. By selecting and integrating the appropriate units, designers will be able to compare their requirements with the capabilities of a range of manufacturing processes. This paper presents a methodology for constructing the data models that will make up these units. A General Purpose data model has already been developed and is presented here, with a discussion of how it forms the basis of the Situation-Specific data models needed for individual units. A method for using these units is also presented, and demonstrated for the case of Selective Laser Sintering. Finally, future work and potential improvements will be discussed.

The paper deals with the issue of the technical control of concurrent engineering projects. A new approach for designing aided-design-control tools is proposed. It is not based on the successive representations of the product to be designed, but on a model of the processes, which guide technical decisions. These processes have been analysed by observation/action in an industrial project and thereafter modelled. Discrepancies due to technical management of projects can then be characterised, helping to define more precisely the needs of designers to obtain technical control of the design process. Requirements for aided-control of the design process have been proposed. Finally, a mock-up of such a tool has been implemented by structuring and capitalising distributed design processes.

The development of Internet technologies supports the design of more efficient collaborative tools. This paper defines a collaborative environment based on theses technologies. It sets the conditions of use of this environment and points out the needs in information sharing. From this analysis we define tools whose functions complete currently available. Two new specific pieces of software illustrate the starting point of this environment development. The first tool, CoDVS, offers functions to archive data shared for the collaboration between actors. The XML format is used to achieve this goal while other functions give opportunities to update project data in a CVS fashion mode. The second tool, CoDISS, allows the dynamic definition of concepts shared by several actors, together with the connection of these data with the working parameters of each actor. Actors collaborate together by accessing this shared database that they can edit. They also automatically update their skill oriented models to reflect changes decided by their colleagues. Updates are automated with an API using the CORBA protocol.

In today’s competitive market, customer satisfaction is the critical factor for success. In addition, the concept of continuous improvement means lower costs and higher profits. The integrated system presented in this paper offers a comprehensive solution for turning customer complaints into an opportunity for success. The system manages relationships with customers, consumers, suppliers, distributors and prospects, tracks complaints, requests and activities resulting from these relationships as well as issues and corrective actions resulting from internal investigations, facilitates communication and provides a specific organization with consistent and easy access to information. Through a customizable workflow, an establishment of ownership, due date reporting and automatic escalations, each customer is guaranteed a timely and thorough response. Continuous improvements occur when problems have been identified, root causes determined and solutions found. The Internal Areas are user defined and can be based on departments, production lines, manufacturing facilities, etc. The Internal Areas are generally concerned with process improvement, product defects and quality audits. The system supports embedded keywords for automatic insertion of database information. This system is a client-oriented interface for integrated design quality systems. It has been implemented in a Romanian company.

Nowadays, time to market becoming shorter and shorter, physical mock up is being more and more often replaced by digital mock up. However physical mock up was very useful to the present day to check accessibility for example. So, it is now important to have tools available to simulate with digital mock up what physical mock up used to be used for. For example, to check accessibility, a tool that allows the simulation of the manipulation of an object by a manikin in a cluttered environment without collision is needed. In this paper, we propose a new way to create human behaviour of a manikin using a multi-agent approach. Our system is based on a former architecture already presented. It consists in a collision-free path planning system using cooperation between software and human operator abilities. The architecture for this co-operation is based on a multi-level tree architecture, which enables the architecture to be completed by adding as many agents as we need. The conflicts between agents are managed by acting on their period of activity. We demonstrate in this paper the fact that collaboration between many agents, each providing the manikin with an elementary behaviour, can provide the manikin with a coherent global virtual human behaviour.